Switchgear cabinets for low voltage typically have a frame composed of profiled bars which are terminated by walls which are connected to them, namely side walls, a rear wall, a top wall and a bottom wall. Situated inside the switchgear cabinet, which can be closed from the outside by means of a door, are with drawable parts which are on different planes and to which electrical units, for example control, switching and regulating units, are in turn applied. These units generate heat which heats the air or gas inside the switchgear cabinet, a thermal convection flow forming inside the switchgear cabinet.
In order to measure the air or gas temperature, a temperature-measuring sensor is situated on each withdrawable part, said sensor being fitted to the base in the upper region of the withdrawable part, to be precise where there is sufficient space for this sensor. This means that, when a unit which is arranged away from the temperature-measuring sensor—and there is optionally another unit between the unit in question and the temperature-measuring sensor—heats up to an impermissible extent, a change in the temperature of the first unit is detected by the temperature-measuring sensor only with a great delay. In this case, it is only determined that the temperature inside the switchgear cabinet has increased; this does not make it possible to detect which unit, if appropriate in which withdrawable part, has reached impermissibly high temperatures.